1. Field of the Invention
The present invention is directed to a process for forming a yarn useful in forming antistatic carpet. More specifically, the present invention is directed to a process for forming a yarn which includes a plurality of nonconductive filaments and at least one conductive filament. Most specifically, the present invention is directed to a process for forming a yarn wherein the conductive filament or filaments are simultaneously co-spun with the nonconductive filaments.
2. Description of the Prior Art
It is well known that static electricity may be generated when a person walks across a conventional carpet formed from synthetic fibrous materials such as nylon, acrylics, polyester, and the like. The discharge of the static electricity when a person is grounded subsequent to walking across such a carpet can be annoying if not discomforting.
One solution to this problem has been to incorporate electrically conductive fibers (hereinafter referred to simply as conductive fiber) into yarns which are subsequently incorporated into carpets to dissipate static electric charges. These conductive fibers typically include a non-conductive fiber-forming polymer as their major component and a conductive material, usually a dispersion of a conductive particulate material in a polymeric carrier.
The prior art has provided a number of methods for incorporating such a conductive fiber into a yarn to impart antistatic properties. For example, U.S. Pat. No. 4,612,150, to De Howitt, discloses a process for combining antistatic filaments and nylon filaments wherein separately spun conductive bicomponent filaments are pneumatically introduced into a freshly spun nonconductive threadline within the quench chimney. U.S. Pat. No. 4,900,495 to Lin discloses a similar antistatic yarn production process wherein a previously formed conductive filament is combined with freshly spun, nonconductive filaments.
Although these processes are useful in producing acceptable products, they have a number of serious drawbacks. First, this procedure is quite expensive, as the separate formulation of the conductive fiber and its subsequent addition in the threadline can add a significant amount to the end product cost. Also, as the addition of the previously formed conductive filament is at the periphery of the nonconductive threadline, intermingling of the conductive filament with the nonconductive filaments is limited. This limited intermingling can have a negative effect on the subsequent processing of the resulting yarn and can result in severe color pollution (due to visibility of conductive filament). Further, since the conductive filaments and nonconductive filaments were separately formed and have different thermal histories, their individual properties, such as shrinkage and crystalline structure are different. These differences can cause breakage of one or more of the conductive filaments during processing. More specifically, it is noted in the description of the '150 patent found in the '495 patent that the spinning and winding speed of the nonconductive filaments are established so that the conductive filaments will not break when they are drawn at the same ratio as is required for the nonconductive filaments.
A need, therefore, exists for an improved antistatic yarn production process which overcomes these and other deficiencies which are inherent in the prior art processes.